218 THE VOYAGE OF H.M.S. CHALLENGER. 



joints. The following pinnules are of about the same length, but the joints gradually 

 increase in size and diminish in number, still remaining much wider than long. Tn the 

 pinnules of the fifteenth and several of the following brachials the fourth and fifth joints 

 are considerably wider than their fellows, but in the later pinnules the joints are longer 

 than wide. 



Disk not much plated, except along the ambulacra. There is a strong covering 

 of plates over the genital glands, with numerous sacculi imbedded in it ; and the later 

 pinnules have a well-defined ambulacra! skeleton, the sacculi alternating with the side 

 plates. 



Colour in spirit, — a light whitish-brown, with a brownish-gre}?- ventral perisome. 



Disk 10 mm.; spread about 55 cm. 



Locality. — Station 192, September 26, 1874 ; near the Ki Islands ; lat. 5° 49' 15" S., 

 long. 132° 14' 15" E.; 140 fathoms ; blue mud. Four specimens. 



Remarks. — Two of the four representatives of this fine species have but ten arms 

 each, and they thus find a place in the Basicurva -group, as has been already noticed on 

 p. 128. A third, that figured on PI. XLIL, has three distichal axillaries on separate 

 rays ; while the fourth has one normal distichal series and two others on a ray which 

 has been regenerated from the second radial. 



The tendency of the centro-dorsal to assume a columnar shape, and the arrangement 

 of the cirri upon it in five double rows beneath the rays, are points of resemblance 

 between this species and Antedon quinquecostata from the same locality (PI. XXXVIII. 

 fig. 1); but they are very different in other respects. Antedon quinquecostata has slender 

 and spiny cirri composed of many joints ; while those of Antedon fiexilis consist of but 

 twenty-five smooth and relatively stout joints. The tubercular nature of its rays and 

 arm-bases is also a good distinctive character ; while it has extremely abundant sacculi, 

 although these structures are most scantily developed or even altogether absent in Antedon 

 quinquecostata. Not only do they alternate with the side plates of the pinnule-ambulacra, 

 but they are very abundantly distributed over the plated coverings of the genital pinnules 

 which are unprovided with ambulacra, as in Antedon incisa (PI. XXI. fig. 2a) and 

 Antedon angusticalyx (Part I. pi. liv. fig. 5). 



Attached to the under side of the centro-dorsal of one specimen is a Brittle- Star which 

 seems to belong to the genus Opliiomusium, so far as I have been able to make out its 

 characters from a view of the dorsal surface only. But I cannot refer it to any species 

 of this genus, or to any other Ophiuran which was obtained by the Challenger. It has a 

 relatively large dorso-central, five small basals, and five large radials, the other ends of 

 which are tubercular, and fit in between the two large radial shields which are also more 

 or less tubercular on their line of junction. The arms of the Brittle-Star extend outwards 

 between the cirri of the Comatula and coincide in direction with its rays, while their 



